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Animal Structure and Function

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Chapter 36 Animal Structure and Function


I.                     Levels of Structural Organization

a.      Cells working together in unison are considered a tissue.

b.      Several tissues working together are called an organ.  Different types of tissue have different structures to improve their function.

c.      Several organs working together are called an organ system

d.      Several organ systems working together make an organism.

II.                   Tissues are divided into four main categories

a.      Epithelial Tissue

                                                               i.      Covers the outside of the body

                                                             ii.      Lines organs and internal cavities

                                                            iii.      Closely joined

                                                           iv.      Acts as a barrier to injury, organisms, or fluid loss.

                                                             v.      Free surface is exposed to fluid or air.

                                                           vi.      Cells are attached to a basement membrane which is a dense mat of extracellular matrix that holds the cells in place.

                                                          vii.      Divided into several smaller categories

1.      Simple epithelium made of one layer.  Only one layer of cells is touching the basement membrane

2.      Stratified epithelium made of many layers of cells and only one layer is in contact with the basement membrane.

3.      Pseudostratified epithelium Appears to have multiple layers because the cells are elongated but all cells involved touch the basement membrane.

                                                        viii.      Shape

1.      Cuboidal cube shaped

2.      Columnar bricks

3.      Squamous flattened

                                                           ix.      Also absorb or secrete chemical solutions like the mucous membrane.

b.      Connective tissue

                                                               i.      Binds and supports other tissues.

                                                             ii.      Sparse population of cells scattered throughout the matrix.

1.      Matrix consists of a web of fibers embedded in a uniform foundation that may be liquid, jellylike or solid.

                                                            iii.      Made of three kinds of proteins

1.      Collagenous fibers made of collagen that are nonelastic and do not tear easily when pulled lengthwise.

2.      Elastic fibers long threads of elastin and provide a rubbery quality that lets the tissue return to its normal shape.

3.      Reticular fibers very thin and branched, composed of collagen and join connective tissue to adjacent tissues.

                                                           iv.      Six major types

1.      Loose connective tissue binds epithelia to underlying tissues and functions as a packing material.  Contains all three types of fibers.

a.      Examples are fibroblasts, which secrete the protein ingredients of the extracellular fibers, and macrophages that engulf bacteria and debris of dead cells by phagocytosis.

2.      Adipose tissue Stores fat throughout the matrix, which pads and insulates the body.  Contains a large fat droplet that swells when fat is stored and shrinks when it is used.

3.      Fibrous connective tissue Dense due to collagenous fibers.  Arranged in parallel bundles that maximizes nonelastic strength.

a.      Examples are tendons that join muscle to bone and ligaments that join bone to bone.

4.      Cartilage Made of collagenous fibers embedded in a substance called chondroitin sulfate that is secreted by Chondrocytes.  These cells are found in the lacunae making it strong yet flexible.

5.      Bone Mineralized connective tissue formed by Osteoblasts that deposit a matrix of collagen as well as calcium, magnesium, and phosphate ions, which harden within the matrix.  Forms in repeating units called halversian canals that contain concentric layers of the matrix surrounding a central canal containing blood vessels and nerves.  Osteocytes are found in the lacunae and destroy old bone matter and replace it with new matter to improve the strength.  The interior is spongy bone tissue filled with bone marrow that manufactures red blood cells.

6.      Blood does not have an extracellular matrix but is made of liquid called plasma containing water, salts, and dissolved proteins.  The plasma contains erythrocytes or red blood cells and leukocytes or white blood cells.  It also contains platelets that help with clotting.

c.      Nervous tissue

                                                               i.      Senses stimuli and transmits signals from one part of the animal to another.  The functioning unit is called the neuron, which is made of a cell body containing the organelles and dendrites, and axons, which transmit the signals.

1.      Dendrites transmit impulses from their tip toward the rest of the neuron.

2.      Axons transmit impulses toward another neuron or toward an effector.

d.      Muscle tissue

                                                               i.      Composed of long cells called muscle fibers that are capable of contracting when stimulated by nerve impulses.

1.      Arranged in parallel and made of microfilaments called actin and myosin.

2.      Three types of muscle exist.

a.      Skeletal muscle, which is responsible for voluntary movements of the body.  It is also striated because of the overlapping filaments.

b.      Cardiac muscle forms the heart.  It is also striated but branched and then ends are joined by intercalated discs, which relay signals from cell to cell.

c.      Smooth muscle lacks the striations and is found in the walls of internal organs.  Cells are spindle shaped and contract more slowly but remain contracted longer.

III.                  Organ systems are interdependent

a.      Body is made of 11 different organ systems

                                                               i.      Digestive

                                                             ii.      Circulatory

                                                            iii.      Respiratory

                                                           iv.      Immune

                                                             v.      Excretory

                                                           vi.      Endocrine

                                                          vii.      Reproductive

                                                        viii.      Nervous

                                                           ix.      Integumentary

                                                             x.      Skeletal

                                                           xi.      Muscular

IV.                Bioenergetics

a.      Animals are heterotrophs

b.      Obtain chemical energy from food by using enzymes to digest it and then body cells absorb it.  These cells must use cellular respiration to convert the energy to ATP.  Animals are constantly undergoing this process.

c.      The total amount of energy an animal uses is called its metabolic rate and the energy is measured in calories.

                                                               i.      Minimal metabolic rates support the basic functions needed to maintain life.

                                                             ii.      Extremes can cause changes in this metabolic rate.

                                                            iii.      The basal metabolic rate is the number of calories an animal uses at rest with an empty stomach and experiencing no stress.

                                                           iv.      Ectotherms have a standard metabolic rate.

V.                  Regulating the internal environment

a.      Claude Bernard made a distinction between the internal and external environment of an animal.

b.      The internal environment is called the interstitial fluid.

                                                               i.      This fluid fills the spaces between our cells, exchanges nutrients and wastes with blood contained in capillaries.

                                                             ii.      Animals attempt to maintain relatively constant conditions even when the external environment changes.

1.      Temperature

2.      Blood pH

3.      Sugar concentration in blood

4.      Hormones

                                                            iii.      Referred to as homeostasis

1.      Depends on feedback circuits made of a receptor, a control center and an effector.

a.      The receptor detects a change in some variable in the internal environment.

b.      The control center process information it receives and directs and appropriate response.

c.      The effector takes the information about the response from the control center and puts the change into action.

2.      A negative feedback takes place when a change in the variable triggers the control mechanism to counteract further changes in the same direction.  These prevent small changes from becoming too large.

3.      Positive feedback involves a change in some variable that triggers mechanisms that amplify rather than reverse change.  An example is childbirth.

4.      Regulated changes are required for normal body functions.

5.      Often these are cyclic like with changes in hormone levels.